The XFM standard is intended to combine the advantages of M.2 SSDs and BGA SSDs. Kioxia is now launching the flash memory form factor, reminiscent of a memory card, for compact mobile computers, IoT devices, and embedded applications.
The new crossover flash memory (XFM)
The abbreviation XFM stands for Cross (X) Over Flash Memory and was created with the specification JEDEC XFM Device 1.0 was declared the official storage standard last year. The driving force behind this is the JEDEC member Kioxia, who about three years ago, then under the name Toshiba Memory, described a new form factor for small flash memory modules including a suitable slot under the brand name XFMExpress.
At first glance, the 14 × 18 × 1.4 mm (L × W × H) memory module with an area of 252 mm² is reminiscent of a microSD memory card of 11 × 15 × 1.0 mm (L × W × H) but is even more compact. The height of 1.4mm corresponds to the miniSD form factor. The mini memory can hide behind a 1 euro coin.
XFMExress (Photo: Kioxia) However, XFMExpress is actually a new SSD form factor for single-pack models. Until now, Kioxia has served this area with SSDs such as the BG4 series, which measure 22×30mm (L×W) as a pluggable M.2 SSD or in a 16×20mm (L×W) BGA package soldered directly to the motherboard. XFMExpress aims to combine the compactness of BGA with the flexibility of M.2. The modular design with base (2.2mm high) offers the advantages of upgradeability and repairability, which accumulates pluses in durability.
Figure 1 of 7 PCI Express is used as the electrical interface, supporting one, two, or (optionally) four lines (lanes) of the PCIe 3.0 and PCIe 4.0 standards. This results in gross data rates of nearly 1 GB/s (1 lane), 2 GB/s (2 lanes), and 4 GB/s (4 lanes) over PCIe 3.0, or twice the data rate for PCIe 4.0. In the future, PCIe 5.0 will be supported with data rates doubling.
The first products
It is not surprising that Kioxia also makes the first products based on the XFM standard. The Kioxia XFMExpress XT2 series includes 256GB and 512GB memory; previously was promised up to 1 TB. The removable storage uses PCIe 4.0 x2 for just under 4 GB/s gross. The net data rate can be a maximum of 3.5 GB/s but ultimately depends on the NAND flash and controller used. However, no information is available about these latter components. Kioxia describes the key features of XFMExpress XT2 as follows:
- High maintainability – The XFMEXPRESS XT2 enables a new category of small storage devices that are easy to maintain and expand. Combining a robust, compact housing, removable storage functionality and flexibility, the XFMEXPRESS XT2 helps break through technical barriers and design limitations.
- Ideal for mobile devices – The JEDEC XFM DEVICE 1.0 form factor takes up only 252 square millimeters with its small size and low profile (14 mm x 18 mm x 1.4 mm).  It takes up space and optimizes space when built into ultra-compact host devices without sacrificing performance or serviceability. With a minimum device height of just 1.4 millimeters, the XFMEXPRESS XT2 is ideal for slim and light notebooks and opens up new design possibilities for next-generation applications and systems.
- couple – Designed for speed, the XFMEXPRESS XT2 features an interface with PCIe 4.0 x 2 lanes and NVMe 1.4b. The leading industry  The storage device’s performance and robust form factor provide an attractive alternative to other SSD form factors (such as M.2) and enable high-quality computing and entertainment experiences.
Kioxia plans to demonstrate the XFMExpress XT2 at the Embedded World 2022 trade show in Nuremberg (June 21-23) and at the Flash Memory Summit (August 2-4) in California. The press release already talks about the market launch. However, concrete end products that use the new standard are not listed.
She works as an editor at Research Snipers.